This invention relates to mobile agent connectivity.
Mobile agents are devices including laptop and portable computers, personal digital assistants, telephones, and other wireless or personal devices capable of connecting to a network from varied locations. To connect to an Internet Protocol (IP) based network, a mobile agent needs to establish an IP address presence that allows packets to be sent to the mobile agent from arbitrary points in the IP network. However, a purpose of IP addressing is to route packets to a fixed location, and making the destination mobile is at odds with this purpose.
Typically, to establish an IP presence, a mobile agent is in a static subnet that broadcasts, routes, or switches packets to a medium configured to communicate with the mobile agent. The mobile agent may establish an IP presence in a number of ways. The agent may have a statically assigned IP address that an upstream host, e.g., the medium, can directly deliver packets to. If the agent maintains such a static IP address, only subnets recognizing the static IP address may safely be the last step in a communication to the agent.
In another approach, the agent may have a dynamically assigned IP address allowing routing to the appropriate delivery medium that was assigned using a protocol such as dynamic host configuration protocol (DHCP). In this case, a foreign agent that assigned the address is the last step in routing data to the agent.
In a third approach, the agent may be located in a non-IP network, such as telephone company networks, where an IP packet enters the non-IP network through a specific portal and is routed to the mobile agent based upon a global map.
Referring to FIG. 1, under the mobile IP standard propagated by the Internet Engineering Task Force (IETF), a mobile agent 10 can wirelessly and continuously be connected to a network infrastructure 12 using the same IP address regardless of the mobile agent's physical location. The mobile agent 10 is identified by a home address providing information about the mobile agent's home network 14. When the mobile agent 10 connects to the network infrastructure 12 away from its home link 16, the mobile agent 10 is identified by the home address and by at least one care-of address providing information about the mobile agent's current location.
Packets or datagrams sent across the network infrastructure 12 to the mobile agent's home address are transparently routed to the mobile agent's care-of address. The packets or datagrams destined for the mobile agent's home address are received at the home link 16 by a home gateway/router 18 that tunnels the packets or datagrams to the mobile agent's care-of address via an IP tunnel 20. The care-of address may be an address for a foreign gateway/router 22 that forwards the packets or datagrams to the mobile agent 10 over a foreign link 24 that does not use IP routing. As the mobile agent 10 changes physical location and switches to a different foreign gateway/router to maintain connectivity to the network infrastructure 12, the mobile agent 10 updates the home gateway/router 18 with its new care-of address. In this way, the mobile agent 10 can relocate, connect to various foreign gateways/routers, and maintain a constant IP address presence without interruptions or disturbances in network connectivity.